ECN publication
BUCKBLADE: buckling load design methods for rotor blades
Published by: Publication date:
ECN Solar Energy 1-5-1999
ECN report number: Document type:
ECN-C--99-015 ECN publication
Number of pages: Full text:
17 Download PDF  

In the JOULE-III project BUCKBLADE an investigation is performed into theapplicability of several buckling load prediction tools and methods to rotor blade design. This investigation concerns the assessment of the relevant aspects for buckling of rotor blades and consequently collect, describe and validate a number of buckling load prediction methods. Based on several design handbooks and publications a set of so-called 'Design rules' has been formulated. Together with other buckling load predictions methods these 'Design rules' are validated for application to rotor blade design. Part of this validation was based on experiments on two rotor blades that were built and tested within the project. On each of these rotor blades two buckling tests have been carried out. After analysing and comparing the first test results, five parameter studies are performed. The most important conclusions are: (1) For accurate buckling load predictions it is important to have correct values of all orthotropic material properties. This requires tests on batches of material that are made with the same manufacturing process as the rotor blades; (2) All buckling load prediction tools are appropriate for long flat- and curved orthotropic panels under compression. Some tools describe sandwich structures and have shown to be appropriate for buckling load predictions of symmetric sandwiches (sandwiches with equal facings); (3) Omission of the longitudinal curvature and the pre-buckling deformation in calculations for box-type structures under bending leads to an over-estimation of 25% to 35%; (4) Geometric imperfections of the blade structure leads to a reduction in buckling strength. For a geometric imperfection with the shape of the collapse mode and an amplitude of 1% of the wall thickness, the critical load is reduced with 3% to 6%. For sandwich panels with thin facings local imperfections give a strong reduction of the face-wrinkling-buckling load

Back to List